In seismic exploration for surveying on land intense seismic impulses are transmitted into the earth's surface at a desired site and these impulses may be repeated at frequent intervals. A network of geophones is used to sense and to provide a recording of the results at various points in the ground spaced from the site at which the powerful sound impulses are transmitted into the earth. These geophones are coupled to the earth for receiving the seismic energy which has been reflected and/or refracted by sub-surface geologic strata and various other sub-surface structures in the earth and which then returns toward the surface of the earth, where the geophones pick up the returning energy. In this manner, information is obtained about the conditions and characteristics of the geologic formations in the regions being surveyed. Such seismic surveying can be conducted on land, gravel, rocks, marshland, mud, sand, swamps or in shallow water where the land source can be positioned down against the earth.
Such seismic energy land sources have been constructed in a compact and mobile form wherein the apparatus is provided with a tank which may be in the form of an inverted dome provided with a displaceable diaphragm bottom to enclose therein an incompressible liquid such as water. One or more powerful gas-releasing airguns are positioned within the tank and receive and store pressurized air or other suitable gas under high pressure from a source of pressurized gas such as the high pressure receiver storage tank of a high pressure air-compressor. A metal plate is positioned between the diaphragm and the earth so that upon a very sudden or intensely abrupt release of the high-pressure gas into the liquid the flexible diaphragm will suddenly thrust down on the metal plate to displace a portion of the earth beneath the plate to produce a seismic pulse in the earth.
Detailed information concerning prior mobile seismic energy land sources patented by the present inventor is disclosed in U.S. Pat. Nos. 3,800,907 issued Apr. 2, 1974; 3,779,335 issued Dec. 18, 1973; and 3,310,128 issued Mar. 21, 1967.